TABLE XII
PLUTONIUM RELEASE RATES FROM PPO IN WATER
Power
Sample
Wy)
HPZ-3
2.5
Wt
_t&)
Dimensions
Height
6
HPZ-60-3
2.5
6
HPZ-60-2
2.5
6
4
25.
63
19
HPZ-59-4
25.
63
19
HPZ-111-1
2s.
63
19
HPZ-59-2
far. A possible explanation may be accelerated
mm
Days
Diam
Immersed
14
14
14
20
20
20
1115
544
$44
337
337
243
Average
Water
sea
sea
fresh
sea
sea
10°C
37°C
10°C
37°C
10°C
fresh 10°C
Release Rate
_{nCi/m?-s)
20
2.9
155
1.0
15
200
result of faster chemical! reactions at this warm
temperature. Because release rates are based on
plutonium found dissolved or suspended in the
(see Table XII) that the highest release rates are
found in fresh water and the lowest in 37°C
seawater. There is no significant difference that can
be related to the difference in power level between
the 25-W and the 2.5-W pellets.
determine the total plutonium deposited in the tank
by suitable dissolution procedures. Another explana-
designated HPZ-19, were placed 23 m deep in the
ocean off San Clemente Island in March 1973, for
tion of gelatinous plutonium hydroxide on thepellet
cular cylinders, 12.5 mm in diameter by 12.5 mm
plutonium deposition on underwater surfaces as a
water, rapid deposition can reduce the apparent
release rate. At the end of this experiment, we will
tion is that the warm water causes rapid precipita-
surface, forming a protective coating that retards
further release of plutonium.
.
The two 25-W PPO pellets (Table XT) are HPZ-
59-2 at 37°C and HPZ-59-4 at 10°C. After 337 days,
the release rate is 15 nCi/m2-s for the pellet at 10°C,
unchanged from the previous quarter’s rate. This is
the same order of magnitude as the 20 nCi/m2-s
release rate of the 2.5-W pellet HPZ-3 at 10°C. On
the other hand, the amount of plutonium in the
water containing the 25-W pellet at 37°C is very low,
only 2.5 ug. This correspondsto a release rate of 1.0
nCi/m2-s, unchanged from last quarter, the lowest
observed for any heat source in the program, and the
same order of magnitude as the 2.8 nCi/m?-s rate
observed for the 2.5-W pellet in warm seawater
described above. There seemslittle doubt at the present time that plutonium is released much more
slowly into warm seawater than it is into cold
3. In Ocean Immersion Tests. Two PPO pellets,
long-term exposure. The two pellets are right cir-
high, each containing 14.7 g of PuOo. They were
placed on sea bottom debris inside protective
chambersthat permit water circulationbut keep out
animals jarger than one centimeter. The pellets have
been visually inspected at 3-month intervals, then
reimplanted. After 1 yr, they began to be encrusted
with fine sand-like grains. Where the pellet edges are
still visible, no deterioration can be seen, in contrast
to the crumbling of PMC pellets exposed in the
ocean. Plans are being made to remove these pellets
for shipment to LASL in December, where a detailed
examination will be made of them and their encrustations.
F. Clad Sphere in Simulated Seawater
The plutonium release from a 101-W fuel sphere
assembly (FSA), MHFT-13, was measured during
seawater.
immersion for 375 days. Before immersion in the test
2. In Fresh Water. Plutonium release from the
2.5-W pellet HPZ-60-2 to fresh water at 10°C has
averaged 155 nCi/m?-s for 544 days (Table XID.
seawater at room temperature to eliminate the
to 20-nCi/m?-s rates typical of the PPO pellets in
10°C seawater.
Therelease rate from the 25-W pellet HPZ-111-1
has averaged 200 nCi/m?-s for 243 days, which is the
highest value of the three 25-W pellets. It is clear
The FSA gradually became a spotty brown,
This is approximately eight times higher than the 15
14
aquarium, the FSA was cooled in a beaker of
hazard of handling a hot object outside a glove box.
During its immersion in 20°C seawater, we foundessentially no plutonium (less than 10 ng) in the water.
probably becauseof deposition of iron or manganese
hydroxides, but no gross defects were visible.
However, detailed metallography after the FSA was
removed from the water, revealed cladding defects